The present invention relates to a rolling member which is disposed to be rollable or rotatable between members, which are relatively movable to each other, of a rolling bearing, a linear motion guide apparatus, a uniform motion joint or the like.
More specifically, the present invention relates to a rolling member particularly applicable to a rolling bearing having high performance, the rolling member having a line contact structure in place of a point contact structure in a conventional ball bearing, having an effective contact length which is made about ⅔ of a roller while maintaining an easily usable characteristic of the ball bearing and, in addition, having, as like as a roller bearing, four times of load carrying capacity and sixty-four times of usable life time, thereby providing high rigidity, high load carrying capacity and eliminating difficulty in use.
Further, it is to be noted that the ball mentioned herein has a substantially true circular section when cut in any direction and the roller mentioned herein has a cylindrical body having a substantially uniform circular cross section cut in its longitudinal direction.
In a conventional art, balls or rollers are used as rolling members for such rolling bearings.
The ball, in the ball bearing, takes a point-contact structure and, hence, a load capacity is small, but the ball bearing is easily usable and handled. On the other hand, the roller, in the roller bearing, takes a line-contact structure, and hence, has about six times of load (carrying) capacity with respect to the ball bearing. Thus, the roller bearing has high rigidity and high load capacity, but it is necessary to work an object member with high performance and to be assembled with the object member also with high accuracy, thus being not easily usable and being expensive in comparison with the ball bearing.
The present invention was conceived in view of the above circumstances in the prior art and to provide a rolling member capable of being easily usable as like as ball bearing and having high load carrying capacity as like as roller bearing.
This and other objects can be achieved according to the present invention by providing a rolling member which is disposed to be rollable between members which are relatively movable with respect to each other and which is provided with a rolling portion contacting an object member during the rolling motion thereof and longitudinal both end portions, wherein the rolling portion is formed to provide a protruded circular arc shape and the end portions are formed so as to provide spherical shape, the circular rolling portion having a radius of curvature larger than a radius of each of the end spherical portions and a distance between the end spherical portions being larger than a maximum diameter of the circular rolling portion.
In a preferred embodiment of the present invention, supposing that the maximum diameter of the circular rolling portion is defined as a short diameter and a length (distance) between the end spherical portions is defined as a long diameter, the length of the short diameter is within a range of 80xc2x115% of the length of the long diameter.
The circular rolling portion has a large diameter side on one side end spherical portion and a short diameter side on another one side end spherical portion so that the circular shape of the circular rolling portion provides a tapered surface shape in a longitudinal direction of the rolling member.
The circular rolling portion and the end spherical portions are formed to be continuous to each other and this continuous portion between the circular rolling portion and the end spherical portion is formed so as to provide a smooth round shape.
The circular rolling portion is formed by deforming a portion of a material ball and the end spherical portions are opposing two spherical portions of the material ball which are not subjected to the deforming working.
According to the rolling member of the present invention having the structure mentioned above, the contact length of the circular rolling portion is made longer than that of the ball used as rolling member, so that the load (carrying) capacity can be hence made large several times in comparison with the case of the ball, and accordingly, high load capacity and high rigidity nearly that of the roller as rolling member can be realized. Furthermore, the difference in diameter between a central portion of the circular rolling portion and an end portion thereof is smaller than the difference in diameter there between in the case of the ball, so that the differential sliding motion is reduced and the friction resistance can be hence reduced.
Further, the rolling member of the present invention can be smoothly moved in comparison with the case of the ball and less heat generation is caused during the rolling motion.
Still furthermore, since the rolling member can be manufactured from a material ball, the homogeneous structure can be achieved with reduced manufacturing cost in comparison with the case of the roller.
Still furthermore, in the case of the roller, in a case where the track surface is inclined in the roller axial direction, one side of the roller abuts against the object member (for example, rolling member rolling groove), and hence, relatively high dimensional precision is required for the working or assembling of the object member such as track wheel. However, according to the present invention, the rolling portion is formed so as to provide a circular rolling shape, so that the inclination of the track surface of the object member can be considerably allowed as like as the ball. Therefore, it is not required for the object member to have high working or assembling precision.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.